1. Field of the Invention
The present invention relates to an apparatus that dispenses and stirs a test sample and reagent to measure the mixture thereof.
2. Description of the Related Art
An automatic analyzer is an apparatus that dispenses a test sample and reagent and measures the mixture thereof. After dispensing a test sample such as blood or urine and a reagent into a reaction cuvette to cause them to react, the photometry of changes in the color tone caused by the reaction provides a measurement of the concentration and activity of the measured substance or enzyme in the analyte.
This automatic analyzer has a dispensing probe that suctions the test sample and discharges it into a reaction cuvette. Once the test sample is conveyed below the dispensing probe, the dispensing probe is lowered and suctions the test sample by being subjected to negative pressure while immersed within the test sample.
For example, the total amount of collected test sample may be analyzed by the automatic analyzer. In this case, because the capacity of the test sample differs, there is a possibility that the dispensing probe may suction ineffectually if it is not lowered sufficiently. The automatic analyzer is also installed with a large number of test samples, and these test samples sequentially arrive below the dispensing probe and are sequentially suctioned and discharged, so if the dispensing probe is excessively lowered, there is a possibility that the test sample will adhere to the broad range of the outer wall surface of the dispensing probe and the adhering substance cannot be cleaned, thus causing contamination.
Thus, technology for detecting the liquid level of the test samples using an electrical resistance method, or a capacitance method, a pressure detecting method, etc. has been conventionally employed (e.g., Japanese Unexamined Patent Application Publication No. S62-218818).
Herein, in the case of measuring HbA1c (glycated hemoglobin), which is a diagnostic marker for diabetes, the automatic analyzer uses a whole blood sample as the sample to measure absorbance of the sample in which blood cell component that includes hemoglobin has been hemolyzed. In the test sample that includes this blood cell component, the blood cell component settles if left as it is, and the test sample is separated into an upper layer of plasma component and a lower layer of blood cell component. Therefore, ineffectual suction (or suction error) and contamination cannot be resolved by detecting only the liquid level.
Thus, a concept is presented in which the suction position is determined by preliminarily storing the concentration gradient of the blood cell component and estimating the depth from the liquid level to a distribution zone that includes a significant amount of blood cell component, and the dispensing probe is immersed so as to reach this distribution zone (e.g., Japanese Unexamined Patent Application Publication No. 2007-316013).
Additionally, as the shape of the container containing the test sample may differ, a concept is also presented in which the depth of the distribution zone that includes a significant amount of blood cell component is estimated from the shape of the container, the height of the liquid level, and the concentration gradient (e.g., Japanese Unexamined Patent Application Publication No. H11-316239).
However, in the case of a test sample separated into a plurality of layers, a situation of suction error should be prevented in which due to suctioning of the solution in other layers below the desired layer, collection of the test sample has to be performed again. For this purpose, the boundary between the distribution zone of the target component and the upper layer thereof, which is lowered by the suction, should not reach the tip of the dispensing probe that is a suction port by the end of suctioning. Therefore, conventionally, once the target distribution zone has been estimated, the dispensing probe enters deeper with a margin.
In order to prevent contamination, it is desirable for the entry distance of the dispensing probe into the test sample to be as small as possible so that adherence of the test sample to the outer wall surface of the dispensing probe may be reduced and cleaning may be performed sufficiently. If the entry distance is made as small as possible, the error in the suction amount can also be reduced.
However, because the technology described above only estimates the target distribution, there is a possibility that the dispensing probe will excessively enter the test sample in order to avoid suction error, thereby causing contamination. Accordingly, a considerable amount of cleaning time is spent in to ensure full cleaning.